Steering arrangements not having a mechanical connection between the steering wheel and the ground engaging support members are commonly known in work machines. These known arrangements accept steering input commands from the operator through the use of a lever, joystick, steering wheel, or other input device. The steering input commands are transformed to an electric signal that is then transmitted to a controller that sends an electronic signal, responsive to the magnitude of the steering command, to a pump, valve, motor or other mechanical device to turn wheels, speed or slow tracks to actually perform the turning operation.
One example of such a steering apparatus is disclosed in U.S. Pat. No. 4,771,846 issued on Sep. 20, 1988 to Fredrick Venable et al. and is assigned to TRW, Inc. This patent shows a steering system for controlling a vehicle with steerable wheels. The system includes a steering wheel having a steering sensor attached thereto. A signal representative of a desired turning command is transferred from the sensor to a controller. The controller in turn delivers a signal to a hydraulic control valve that controls the flow of fluid to a hydraulic motor that is in turn connected to the steerable wheels.
This steering system also provides the operator with a steering feedback/feel that is provided by an electromagnetic friction brake. The controller in response to a steering wheel position sensor and a steered wheel position sensor controls the electromagnetic brake. The amount of friction force created by the electromagnetic brake depends upon and is limited by the strength of the electromagnet. However this patent is directed towards automobiles that travel at much higher speeds that require constant operator intervention. The patent is also absent any way of dealing with operator fatigue and multi-tasking that an operator of a work machine faces during operation of such a machine.
The present invention is directed to overcoming one or more of the problems as set forth above.